BMW E38 carPC connection

Hello, after lurking a lot on google etc. i finaly think i can get may carpc connected to my car. It is my car pc try so i is supposed to be cheap.

I have 1998 after facelift BMW e38 with 4:3 boardunit that shows modes CD changer/aux/tape/radio and i have DSP with amp. connected to 10+ speakers, NAVI, TV+video unit, telephone unit, cdchanger in trunk, probably also radio tunner, but i didn't found it.

Can you please check "sheme" that i draw if mspaint if ia understand the connection right? Thank you.

Some descriptions are in czech, but it sould not be a problem

I originaly posted this thread to general hardware section, but it probably belongs here.

The quality of the image is not going to be very good, seeing as you are going in with a composite signal, but seeing as you are keeping the orginal screen/system there's not a lot you can do to improve it.

Well it is mainly for mp3 player so if image quality will be good enought for text and albumart it is ok.

Today i dismounted whole accessory installation in trunk and found out that i don't have radio with aux input like i assumed in schema and in wole planing.

So now i wonder if i should go
with tape input for audio - but i assume as i need to have tape in tapedrive that tapedrive will make noise playing it
directly to dsp - not sure about input format and if it is even possible
connect to cdchanger wires and lose cdchanger in trunk - i want to keep it if possible